Eli,
As of this morning, I am experiencing the exact same issue with attempting to open Word documents that I have previously been able to open. I am using IRM hosted by Microsoft, not an internal server. Also, this is happening on multiple machines which leads
me to believe it is an authentication server issue on Microsoft's end since the transition over to the new live account look.
If you discover a work around, please update the thread!
Thanks,
Ronda